The goals of this proposal are to study the differences between cell surface of the different regions of the kidney tubular epithelium with special emphasis being placed on epithelial cell polarity. The establishment of cell polarity and its maintainence by tight junctions will also be studied. Our approach will be to raise monoclonal antibodies against the plasma membranes of the kidney epithelial cell line (MDCK) and kidney plasma membranes. These antibodies will be used as highly specific probes to study the distribution of antigens on the cell surface of kidney tubules in frozen sections by both immunofluorescence microscopy and immuno-electron microscopy. Antigens recognized by monoclonal antibodies will be characterized by immunoprecipitation and SDS gel electrophoresis. Our goal will be to acquire a library of monoclonal antibodies that recognize cell surface antigens on both the apical and basolateral plasma membrane domains and to obtain antibodies which recognize antigens that are specific for different regions of the nephron. These studies should provide further insights into the mechanisms of transepithelial ion, solute and fluid transport. The knowledge gained from these studies can then be applied to the investigation of transport related diseases such as cystic fibrosis and diabetes insipidus.